Managing locks using pg_advisory_locks in python

lock.py

def lock_name_to_int(lock_name):
    """converts lock_name into integer
    This is needed to create a pg_advisory_lock
    Can return negative values, but is acceptable
    """
    return lock_name.__hash__()


def acquire_exclusive_lock(lock_name, log_after_seconds=1):
    cursor = connection.cursor()
    lock_id = lock_name_to_int(lock_name)
    command = "select pg_advisory_lock(%d)" % lock_id
    start = time.time()
    cursor.execute(command)
    acquire = cursor.fetchone()[0]
    time_taken = time.time() - start
    if time_taken > log_after_seconds:
        extlogger.info("ERROR: lock %s - %s getting released in %s seconds (more than %s seconds)" % (
            lock_name, lock_id, time_taken, log_after_seconds
        ))
        print "ERROR: lock %s - %s getting released in %s seconds (more than %s seconds)" % (
            lock_name, lock_id, time_taken, log_after_seconds
        )
    return acquire


def release_exclusive_lock(lock_name):
    cursor = connection.cursor()
    lock_id = lock_name_to_int(lock_name)
    command = "select pg_advisory_unlock(%d)" % lock_id
    cursor.execute(command)
    release = cursor.fetchone()[0]
    if not release:
        raise Exception("Not able to release lock %s - %s" % (lock_name, lock_id))
    return release